Electron discharge device having an anode with improved thermal expansion characteristics



Jan. 5, 1965 w. E. POLSTER 3,164,741

ELECTRON DISCHARGE DEVICE HAVING AN ANODE WITH IMPROVED THERMAL EXPANSION CHARACTERISTICS Filed Feb. 20, 1961 25 37 33 I H A a i 47 J a I[ 4| I 43 a 1 TJL LS- FIG. I

JNVENTOR.

WILLiAM E. POLSTER AT ORNE United States Patent ELECTRGN DESCHARGE DEHQE uavnso AN ANGDE WITH EMPRGVED THERE/EAL E: i -AN- @IQN CHARAtZTERESTHIS William E. Bolster, Evanston, 1nd,, assignor to General Electric (Iompany, a corporation of New York Filed Feb. 2%, i361, fier. No. $6,445 4 (Iiairns. (Cl. 3l3356) This invention relates to electron discharge devices, and more particularly to such devices having an improved anode structure.

Electron discharge devices are constructed having a longitudinally extending cathode, or electron emitting electrode, and a longitudinally extending tubular anode, or electron receiving electrode, surrounding the cathode. If it is desired to have a controlled electron discharge or to have an amplifying device, one or more control grids may be included which may also surround the cathode and be positioned between the cathode and anode.

Such devices are sometimes constructed with the tubular anode having a noncircular perimeter, and having two substantially planar electron receiving surfaces positioned opposite each other. When such a structure is utilized, it has been known to have a longitudinally extending seam along the middle of each such substantially planar surfaces, the seams being opposed to each other and being positioned towards the outer surfaces of the anode and from which flanges or wings extend normal to the planar surfaces. The flanges serve a number of functions, for example, to strengthen the anode structure, to join the portions of the anode, if the anode is constructed of separate parts, to provide mounting means or tabs for the anode, and to serve as heat radiators to cool the anode structure.

However, such structures as have been employed are subject to certain inherent defects. The positioning of the flanges and scams at the center or active portions of the substantially planar anode surfaces, thereby placing the seams opposed to each other and to the longitudinal cathode, creates substantial disturbances in the electric field normally existing in this critical region nearest the cathode. Also, such positioning causes a limitation on the materials from which the anode can be constructed. A material must be chosen which can be formed having a cusp-like longitudinal joint with as short a radius of curvature as possible where the seams are formed, so as to reduce the above-described field disturbances as much as possible. Further, such a device is diflicult to manufacture in that, because of seams, the forming tool can strike the center of such substantially planar surfaces, and accordingly the minor dimension or diameter of the anode structure cannot be accurately controlled or measured. Further, location of the seams and flanges adjacent the active anode surface is to position these in the highest temperature region of the anode. This factor, together with the fact that anchoring of the anodes is desirably effected at the flanges and at points thereon remote from the seams, operates to produce undesired thermal expansion of the anode in a direction tending to decrease the cathode-to-anode distance. This, of course, adversely affects operation of the device, especially in such devices having high perveance and correspondingly critical cathode-to-anode spacing.

It is, therefore, an object of this invention to provide an electron discharge device having an improved anode structure.

3,164,741 Patented Jan. 5, 1965 "ice It is another object of this invention to provide an anode structure for an electron discharge device whereby the electric field established between the anode and the cathode is substantially undisturbed in any critical region thereof.

It is a further object of this invention to provide an anode structure for an electron discharge device which is simple to manufacture to desired close tolerances and which is free of any undesired thermal expansions in the region adjacent the active anode surface thereof.

Briefly stated, and in accordance with one embodiment of my invention, an electron discharge device having a noncircular tubular anode structure is provided, the anode having a major and minor axis and in which the longitudinally extending seams and flanges of the anode are disposed between the major and minor axes of the anode and offset or noncoplanarly arranged with respect to each other, thereby providing, in the critical active anode regions adjacent the cathode, a smooth and continuous anode surface.

For a better understanding of the invention, reference may be had to the accompanying drawing, in which:

FIG. 1 is a perspective view, with parts broken away, of an electron discharge device having an electrode structure according to one embodiment of my invention;

FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1 with certain parts omitted in the interest of clarity;

FIG. 3 is a view similar to that of FIG. 2 illustrative of a modified form of electrode structure which can be used in the electron discharge device of FIG. 1; and

FIG. 4 is a similar view of another modified electrode structure according to my invention.

Referring now to the drawing and particularly to FIGS. 1 and 2 thereof, there is shown an electron discharge device Which comprises a longitudinally extending cathode 11 which may be of the indirectly heated type and which is disposed coaxially with the longitudinal axis of the device. It will, of course, be understood that where the principal features of this invention are embodied in devices consisting of plural tube arrangements, the coaxial arrangement of the cathode and the axis of the tube may be dispensed with in favor of displacement of the tube units from the axis of the device. Surrounding the cath ode is a control electrode or grid 13 which may be of the wire-wound or frame grid variety, as desired, and surrounding which is a tubular anode 15, the cathode grid and anode elements being supported between insulative spacers or micas l7 and mounted in an evacuated glass or other suitable material envelope 19.

In the embodiment illustrated in FIGS. 1 and 2, the cross-sectional shape of the tubular anode 15 is generally rectangular having slightly rounded or bevelled corners and thus may be characterized by a minor axis 21 and a major axis 23 (FIG. 2) with the axis of the cathode 11 being located at the intersection of the minor and major axes 21, 23.

The anode 15 may be formed of two complementary sections, each having a relatively Wide lateral wall portion as at 25 and 2.7 and a relatively narrow lateral wall portion as at 29 and 31. The sections are formed with similar end wall portions 33, which, together with the lateral wall portions, define the generally rectangularly shaped anode electrode 15. As shown, the lateral wall portions 25, 2.7, 2.9, and 31 are'forrned with flanges or Wings 37, 39, 41, and 43, corresponding pairs of which are suitably joined along the lengths thereof as by staking,

spot welding, or the like thereby to form a unitary anode structure having two longitudinally extending seams 45,

and on opposite sides thereof. It will be noted further that the seams and corresponding flanges or wings are positioned, in accordance with this invention, beyond the 'lateral ends of the cathode 11 as viewed along the longitudinal axis of the device. In this manner, the active surfaces of the anode are free of seamsand associated flanges and are effectively smooth, continuous and substantially planar. a 7

It will be observed that the structural arrangement of the seams 45, 47 and associated flanges, in relation to the location of the cathode 11, provides a cathodeto-anode space in the region of the active surfaces of the anode that is virtually undisturbed by abrupt discontinuities so that the electric field established in this space is likewise free of any abrupt discontinuity. In this manner, the desired operation of'the device is enhanced while at the same time facilitating the determination or accurate measurement of interelectrode spacing between the cathode andthe anode.

For securing the anode 15 in the spacers 1'7 there are provided at the extremities of the flanges tabs or cars 49 which are provided at a medial portion thereof with embossments 51 of such size and shape as to be snugly received, together with the tabs, in conformed openings provided in the spacers 17. it will be observed that anchoring of the anode is thus accomplished by the tabs at the extremal portions of the flanges. ltwill be noted further that in view of the offset position of theflanges relative ,to the active anode surfaces, the production of localized hot spots at the active surfaces can result in thermal expansion thereof mainly in a direction parallel to the wide dimension of the anode. Such expansions have little or no effect on the interelectrode radial spacing between the anode and the cathode and, accordingly, does not affect the dynamic characteristics of the device. This is in marked contrast to devices heretofore employed which the flanges and seams are disposed coplanarly, the common plane of which intersects the axis of the device and of the cathode. In such prior known devices and because anchoring of the anode is accomplished at the flanges and at points therein remote from the seams 45, .4? thermal expansion of the active surfaces is produced in a radial direction tending thereby to change the interelec- .trode spacing. Such changes in spacing are known to have resulted in unwanted alterations of the dynamic characteristics of thedevice.

PEG. 3 which may be utilized in the device .of FIG. 1. As shown in FIG. 3, an anode electrode 53 is provided having certain features in common with that of the embodiment of FIGS. 1 and 2 and, to that extent, similar reference numerals are employed. In this embodiment however, the flanges 55, 57 and associated seams 59, 61, instead of being disposed onopposite sides of the minor axis 21, are disposed on the same side thereof and in coplanar array.

However, the plane of the flanges and the plane including I lfrom, however, in that the anode assembly instead of being formed of two complementary sections, is shown as formed of a single sheet of conductive material which is bent to provide the desired configuration as at 63. Other parts of the anode structure shown in FlG. 4 which are similar to corresponding parts of FIGS. 1 and 2 are identified with similar reference numerals.

There has thus been described several embodiments of the invention wherein portions of an anode electrode which are nearest the cathode of an electron discharge device are smooth and continuous surfaces, and hence permit the establishment of a resultant continuous electric field in these critical areas. Also, the anode arrangements shown permit the use of materials which have previously been unavailable for use in anodes in the prior art. This is so because the seams formed by the noncoplanar flanges are positioned in less critical regions of the anode and, as a result, materials can be used which have more desirable physical characteristics. In addition, such anodes are easier to manufacture in that forming tools can now strike the center of the primary electron receiving surfaces and anodes can be manufactured to more accurate tolerances.

, While the invention is thus described and several embodiments illustrated, it is intended that the invention should not be limited to only these illustrative embodiments. Instead, many modifications will be obvious to those skilled in the art which would lie within the spirit and scope of the invention. 1 For example, the invention is not limited to use with tubular anodes having a substantially'rectangular cross section, as shown, but instead may be used with any anode surface having a noncircular continuously closed surface. Instead, it is intended that the illustrates a modified form of anode structure the minor axis are spaced a distance sufiicient to locate the flanges in a region beyond the extremity of the cath-' ode 11. It will thus be noted that the advantages described above and residing in the fact that a substantially continuous and smooth active anode surface is provided which may readily be determined and measured with respect to the anode. Also, the undesired thermal expansion of the active surface of prior-known devices is here also avoided as is the production of'unwanted electrical field disturbances. a

FIG. 4 illustrates still another modified form of anode structure according to my invention. The embodiment of b FIG. 4 is similar to that of FIGS. 1 and 2, differing thereinvention be limited only by the appended claims. What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electron discharge device comprising a longitudinally extending cathode, a longitudinally extending tubula r anode surrounding said cathode and having a noncir- 'cular cross section, said anode having two substantially planar electron receiving surfaces of which the central portions normally are heated to excessively high temperatures, said anode being formed of sheet material to provide oppositely-directsd radiators next adjacent said electron sheet material and including flanges on said electron re-.

ceiving surfaces, said flanges and said surfaces meeting in longitudinally extending seam portions, one of said'seam portions each being substantially aligned with one edge of said cathode, the other of said seam portions being substantially aligned with the other edge of said cathode.

3. An electron discharge device comprising a longitudi nally extending cathode, a longitudinally extending tubular anode surrounding said cathode, said anode and said cathode havingnoncircular perimeters, said anode having two substantially planar electron receiving surfaces and longitudinally extending flanges on said electron receiving surfaces offset from each other and from a first plane extending through the longitudinal axis of said cathode and which is normal to said substantially planar electron receiving surfaces and from a second plane extending through. said longitudinal axis and which is normal to said first plane.

4. An electron discharge device comprising a longitudinally extending cathode, a longitudinally extending said cathode and the other said flange substantially aligned tubular anode surrounding said cathode, each having subwith another edge of said cathode.

stantially parallel noncircular perimeters, said anode hava ing two substantially planar electron receiving surfaces Balsam Chad m m6 fila of thls Patent normally subject to relatively high operating temperatures, 5 UNITED STATES PATENTS said anode being formed with flanges projecting outwardly 2 145 400 Loppacker Jam 31, 1939 from said electron receiving surfaces and disposed with 2 724 071 Larson NOV 16, 1955 one said flange substantially aligned with one edge of 2 799,796 Vermettg et 1 July 1 19 

1. AN ELECTRON DISCHARGE DEVICE COMPRISING A LONGITUDINALLY EXTENDING CATHODE, A LONGITUDINALLY EXTENDING TUBULAR ANODE SURROUNDING SAID CATHODE AND HAVING A NONCIRCULAR CROSS SECTION, SAID ANODE HAVING TWO SUBSTANTIALLY PLANAR ELECTRON RECEIVING SURFACES OF WHICH THE CENTRAL PORTIONS NORMALLY ARE HEATED TO EXCESSIVELY HIGH TEMPERATURES, SAID ANODE BEING FORMED OF SHEET MATERIAL TO PROVIDE OPPOSITELY-DIRECTED RADIATORS NEXT ADJACENT SAID ELECTRON RECEIVING SURFACES, THE JUNCTION OF SAID RADIATORS AND SAID SURFACES DEFINING TWO LONGITUDINALLY EXTENDING SEAM PORTIONS, SAID SAME PORTIONS BEING OFFSET FROM EACH OTHER AND FROM THE SAID HIGH TEMPERATURE PORTIONS AN AMOUNT SUFFICIENT TO MINIMIZE DISCONTINUITIES IN SAID ELECTRON RECEIVING SURFACES AND SIMULTANEOUSLY TO EFFECT HIGH HEAT RADIATION THEREFROM. 